http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500082

Flora of North America accepts only two varieties: var. quinquefolia and var. minima. Both are now accepted at species level: Anemonoides minima and Anemonoides quinquefolia.

http://www.plantsoftheworldonline.org/taxon/urn:lsid:ipni.org:names:13540-2

POWO lists Anemone quinquefolia var. bifolia as a synonym.